HONG KONG • The United States' plans to send warships or military aircraft within 12 nautical miles of China's artificial islands in the disputed South China Sea, possibly within days, could open a tense new front in Sino-US rivalry.
A range of security experts said that Washington's so-called freedom of navigation patrols would have to be regular to be effective, given Chinese ambitions to project power deep into maritime South-east Asia and beyond.
But China would likely resist attempts to make such US actions routine, some said, raising the political and military stakes.
China's navy could, for example, try to block or attempt to surround US vessels, they said, risking an escalation.
Given months of debate already in Washington over the first such patrol close to the Chinese outposts since 2012, several regional security experts and former naval officers said that the US government might be reluctant to conduct them often.
US allies such as Japan and Australia are unlikely to follow with their own direct challenges to China despite their concerns over freedom of navigation along vital trade routes, they added.
"This cannot be a one-off," said Dr Ian Storey, a South China Sea expert at Singapore's Iseas-Yusof Ishak Institute.
"The US navy will have to conduct these kinds of patrols on a regular basis to reinforce its message."
The Obama administration has said that it would test China's territorial claims to the area after months of pressure from Congress and the US military. It has not given a timeframe.
"I think we have been very clear - that we intend to do this," Mr Mark Toner, the State Department spokesman, told reporters last Monday.
Chinese Foreign Ministry officials said this month that Beijing would "never allow any country to violate China's territorial waters and airspace in the Spratly islands in the name of protecting navigation and overflight".